Reprise on nuclear fuel rod coolant requirements

In a recent post by Robert Wood (now lost somewhere in cis-lunar space) I recall a statement to the effect that hot fuel rods placed in a water bath would cool down enough in a few days to require at most replacement of evaporated water in the bath.

How is this compatible with the quote below from the AF's Midnight Crossing article?

Even if handled well, loss of power and cooling at the numerous waste pools where atomic fuel rods are kept could cause the water to boil away and permit the release, into the local atmosphere, of lethal levels of radioactivity. Recently loaded rods-those placed in the waste pools within the past two years-could begin to melt down within 48 hours of a loss of power.

Hmmm. I think this is the difference between a half-empty pot and a
half-full one.

Wat was posted about reactors was that after a short cool-down
period, all that was needed to keep it safe was to keep the core
coolant water topped up. The residual heat is removed by water
boiling. Letting it boil dry would leave no cooling and a disaster in
the making, but that would require complete long-term dereliction of
duty by the reactor operators. If all else failed, water could just
be tipped in by the bucketfull.

Much the same would appear to be true for waste storage. I think its
just spun differently (anti-nuke rather than pro-) If the 48 hour
figure is true, it suggests that the storage pools should be made
rather larger (so they'd take longer to boil dry).

You might want to consider a kettle element. Immersed in water, it
simply boils. Allow the water to boil away and (if the power cutoff
fails) the element will melt down.

I seem to remember that the heat output of a nuke core after 2 days
was quoted here as .005% of operational. If the nuke generates 500MW
normally, that's 25kW, or about ten UK household kettles.

This is all very interesting....if you understand it. I know I am
not the ONLY dummy on this forum. Lets cut to the chase. If a nuke
has to be suddenly shut down, is it 4 days or 4 months for cooling.?
And will the public even be ALLOWED to know about it??

Taz...whose old brain just gets less wrinkles while the face gets
more.

What Robert Cook posted has nothing to do with Chernobyl-class
reactors.

This thread refers to Russian nuclear reactors, right? So confusing
the picture with yada yada about a completely different scenario is
just a well-known trolling technique from Anita who speculates
that it would go by unnoticed by innocent, uninformed lurkers.

Concerning the NRC decision for US reactors "Y2K-Ready to Crash"
we will all have to wait to see how it unfolds when the EPA, the
Ralph Naders of this world, and plain constituents jump into the act.

If violation of proven safety regulations and quality assurance
protocols prevail, it is just asking for Three Mile Island-type
catastrophes to happen. DO NOT COMPLAIN later. As y2k has duly
proven, time cannot be rewinded nor post-poned.

Take care and get involved. If you don't care nobody else cares
either.

You're getting funnier. You wrote: "This thread refers to Russian
nuclear reactors, right? So confusing the picture with yada yada
about a completely different scenario is just a well-known trolling
technique from Anita who speculates that it would go by unnoticed by
innocent, uninformed lurkers."

I never even READ the "Midnight" or whatever thread to which the
poster referred. He mentioned something about core cooldowns and I
remembered having read a thread wherein Robert mentioned it. I
simply provided a link to that thread. If it wasn't the one the
poster wanted, I don't think I'm to blame for that. You can't blame
your bad hair days on me ALL the time, George.

George (or anyone!)-- Are fuel rods in a Chernobyl-type reactor
hotter than fuel rods in PWR/BWR-type reactor?

The recent NRC report on U.S. reactor compliance indicates that some
35 reactors here are not yet compliant, but the systems enabling safe
shutdown are compliant. I read in this the possibility that some of
these may shut down if the distribution system has problems. If any
of them actually do shut down, the length of time it takes to cool
the cores below the danger point is a real question, given other
possibilities such as lack of fuel for emergency generators.

The answers given relate to the usual design practices for a US/UK/Canada/France/Germany/Spain/japanese/Korean reactor and cooling pool/refueling pool design using the "western" design practices.

These require spacers between the fuel assemblies, set the minimum and maximum pool depths, time between refueling and fuel transfer, backup power supplies and emergency generators, backup fuel pool and refueling pool cooling systems, and backup service water systems. These are light-water and heavy water (Canada) systems using thermal nuetrons in a water-moderated, water-cooled reactor with zirconium-clad fuel assemblies.

Under these cases, the calculations stand as written. 3-4 days to cool to room temperature. Decay heat from the core load declining to neglible levels in a few weeks, fuel storage pool able to be cooled by any number of emergency coolers, bypass pumps, or simple water replacement. The specific alternate paths will vary at each facility, but there are usually four designed modes using different emergency generators or alternate on-site power supplies, and another 3-6 alternate (manually configured) modes.

While the nuclear physics involved in radioactive decay of spent fuel is universal, the specific design criteria for a Russian-designed plutonium weapons breeding reactor like Chernobyl is fundamentally and mechanically totally different. I'll look up the design of the Chernobyl reactor building(s) and try to get spent fuel storage drawings, but the part of the drawings released and available so far has been the core and steam generation areas of the plant - not the fuel handling and storage.

(Since these two areas are directly related to plotonium production for the Russian nuclear weapons program, I'm not positive I'll be able to get the actual drwings even then! Ever here of a little group called the KGB?)

Until I see either the Russia load factors in their fuel pools, and the sizes and shapes of the pools themselves, plus the specific Russian graphite-moderated fuel assemblies - I'm not going to make assumptions about what they (the Russians) have done in the past (when they had money) and now, when they are broke and desperate. It may be this bad, they (the writers) may be exaggerating. I know I can't tell you for sure which is true - nor (if true) at many facilities it may be this bad - not all reactors are operated the same way over there.

Let Ted Turner, Al Gore and the Democratic socialists assume the Soviets are the world's environmental heroes and the US is the world's villian - I know the utter distain they have for people's lives, their children's safety, and the safety of anybody who oopses them.

Anita, my apologies. No strings attached. I just blew some steam off.
Sorry. Still virtual friends?

What happened was that I took for granted Anita that, without
necessarily going into the "Midnight Crossing" link, you had still
read in the original post that the question revolved about Russian
nuclear reactors, not US. Still, it's o.kay, I for one may that sort
of mistake every day, more than once. So your input was still good
and valid and we all thank you for it. You see Anita, I'm no bully...
please no hard feelings.

Now, down to business

Tom, the short answer to your question is "It doesn't matter".
Fuel rods in Chernobyl class reactors could be hotter or cooler
(give or take a couple of hundred degrees C) than PWR/BWR-type
reactors. What DOES matter is the completely different scenario.
One thing is the USA, the NRC, bla, bla, and another completely
DIFFERENT thing is Russia and Chernobyl 'technology'.

As your own "Midnight Crossing" link clearly leaves on record, Russia
today fails miserably in many things that affect the subject matter
at hand, be it command and control nuclear structures, decision-
making, logistics, scheduling, planning, pirated
software/hardware/firmware, half-forgotten program languages, very
old computers, failure in telecommunications, in electric power
generation, distribution and supply, banking (tens of thousands of
nuclear scientists who have not been paid regularly in years!)
political and economic upheaval, mafias, disruption of nuclear
facilities by thieves, non-performing diesel generator back-ups,
etc., etc. So all of these problemas, plus the serious impairment in
tracking the reactor's facility's status, make recovery all but
impossible. Read it, it's all in your own link. Melt down of loaded
rods within 48 hrs. of loss of power is for REAL. Then we have that
only 25% of Russian nuclear material is under control. And of course
that safe shutdown still means millions will freeze to death.

Anita, Tom, also please read carefully the last 10 paragraphs (they
are real short, average of 5 lines each) which tie-in with many other
y2k items of debate.